For certain electronic devices, it is particularly important to protect against physical tampering after the device has been sold or distributed to an end-user. For example, tampering is of particular concern for devices that store or process sensitive data and for devices having functions or capabilities that incentivize unwanted, unauthorized intrusions into the devices. For example, a payment terminal may process payment transactions, and may interact with payment devices such as a payment card having a magnetic strip that is swiped in a magnetic reader of the payment terminal, a payment device having a Europay/Mastercard/Visa (EMV) chip that is dipped into corresponding EMV slot of the payment terminal, and near field communication (NFC) enabled devices such as a smartphone or EMV card that is tapped to the payment terminal and transmits payment information over a secure wireless connection. The payment terminal may receive payment information from the payment device as well information about a transaction, and may communicate this information to a payment system for processing of the transaction.
As of a result of its central role in the transaction processing system, the payment terminal is a prime target for third party attackers attempting to access payment information, process fraudulent transactions, and otherwise engage in fraudulent activities or theft. In many cases, the attackers attempt to physically access components of the payment terminal, such as one or more communication lines carrying data or a processor that communicates and processes payment information. Attackers may attempt to eavesdrop on signals (e.g., a passive attack) or to modify or spoof payment processing communications (e.g., an active attack) by injecting malicious signals into the payment terminal.
In an effort to thwart physical attacks, payment terminals may implement tamper detection devices such as tamper meshes and tamper switches. For example, if an attacker attempts to remove the cover of the payment terminal, a tamper switch may open. A traditional tamper detection technique in an electronic device is to enshroud the sensitive components (e.g., processor or other circuitry of payment terminal) within the device with a tamper mesh. The tamper mesh is connected to an electrical power source and to a detector within the device. If an attacker attempts to access the sensitive components (e.g., by drilling a small hole into the payment terminal), the conductive trace may be broken, resulting in an open circuit. The detector may sense an open circuit of the tamper switch or tamper mesh, which may shut off the payment terminal or trigger another appropriate countermeasure in response.
While such techniques provide tampering protection from legitimate tampering attacks, it is also possible that certain acts, such as unintentional handling of the device, or even the environment in which the device operates may trigger an unwanted tamper response.